Burglar alarm



Patented Nov. 22, 1932 UNITED STATES BLANCHARD BOYLE, OF INDIANAPOLIS, INDIANA BURGLAR ALARM Application filed May 11, 1931. Serial No. 536,631.

This invention relates to burglar alarm systems and is designed .primarily for use in banks and similar situations in which the banker or other person would give the alarm by raising his hands at the command of the burglar or robber.

The object of the invention is to provide a burglar alarm system of this type in which there will be nothing to indicate to the burlo glar the existence of the system and which will be effective in giving a suitable signal or alarm as desired.

Referring to the accompanying drawing, which is made apart hereof and on which similar reference characters indicate similar parts,

Figure 1 is a view of a bank room showing the system installed therein,

Figure 2, a section on line 22 of Figure 1,

-Figure 3, a diagrammatic view of the amplifying circuits forming a partof the system.

The purposes of the invention are carried outby providing a light sensitive cell in circuit with suitable amplifying and relaying circuits and with a constantly burning light shining upon the cell arranged so that any interruption to the ray of light will cause the electric circuits to give the necessary alarm or signal by an electric hell or other electric signal device.

In the drawing numeral 10 indicates a bank building or room with side walls and a ceiling and having a window 11 behind which the .bank clerk usually stands. Positioned somewhat to the right and slightly above the level of the bank window is an electric or other light 12. At the rear of the room is positioned a light sensitive cell 13. The cell must be so positioned as to permit a ray of light to pass uninterruptedly at all times from the lamp 12 to the cell, i. e. it must be above the normal height of ,the employees of the bank so that in passing to and fro in the room the light will not be interrupted. The cell may be of any suitable light sensitive substance'such as caesium magnesium which acts as a conductor only when exposed to light. The minute current through the cell 13 is .has been sounded. The system therefore not line 17 and 18 is in circuit with an electric bell 19 which circuit is closed by a switch 20. Lines 21 and 22 in circuit with the power 6 transformer 15 energize a solenoid 23 normally to hold the switch 20 open. A suitable manually controlled resistance element 24 is connected in the line 22.

In operation when the light is shining upon the light sensitive cell 13 the circuit is closed, and the current is amplified to energize the solenoid 23 and to hold the switch 20 open. If an attempt is made to hold up the bank the first move made by the banker of course 7.0 is to throw up his hands and in doing so there is a tendency for the hands to move outwardly. When he does this, his right arm will interrupt the ray of light passing from r the lamp 12 to the light sensitive cell 13. This destroys the conductive power of the cell and opens the circuit which in turn deenergizes solenoid 23 and permits the switch 20 to close. When this switch closes it closes a circuit through the lines 17 and 18 to ring the alarm bell 19. Obviously the alarm 19 may be positioned anywhere. desired either in an .adjacent building, in the police headquarters or any remote place where an alarm may summon the necessary help. It should be noted that the signal will be given with out any notice to the robber or without anything by which he may suspect that an alarm only is effective in sounding the alarm but minimizes the danger of exciting the would be robber to kill the bank clerk as he would do if suspicious that an alarm would be given without any notice to the robber or without anything by which he may suspect that an alarm has been sounded.

It will be obvious to those skilled in the art that various'changes may be made in my device without departing from the spirit of the invention and therefore I do not limit myself to what is shown in the drawing and described in the specification, but only as indicated by the appended claims.

Having thus fully described my said invention, what I claim as new and desire to secure by Letters Patent, is:

1. The combination with a room having a single window therein of a burglar alarm comprising an electrically operated alarm device, an electric circuit for operating said alarm, a light sensitive cell mounted on the rear wall of said room in control of said circuit, and a constantly illuminated light mounted above said window for rendering said cell active, the circuits being so arranged that interruptions of said light falling on the said cell by a persons raised hands will cause operation of the said alarm, substantially as set forth.

2. A burglar alarm adapted to be used in a room of the kind described comprising a signal giving device, means normally holding said device inactive, a light sensitive cell positioned on the rear wall of said room in control of said means, a constant source of light positioned on the front wall for rendering said cell active, interruption of the light causing operation of the said signal giving device, substantially as set forth.

3. The combination with a room having a single window therein of a burglar alarm comprising an electrically operated bell, a

circuit to said bell, a switch in said circuit,

said switch being biased toward closing position, a solenoid for holding said switch open,.

a light sensitive cell mounted on the rear wall of said room, an electric light mounted on the front wall above said window for rendering said cell active, said light and'cell being positioned so that a person moving about said room will not interferewith the light rays to the cell and any interruption of said rays by a persons raised hands will cause the alarm to be sounded, substantially as set forth.

In witness whereof, I have hereunto set my hand at Indianapolis, Indiana, this 9th day of May, A. nineteen hundred and thirty-one;

QBLANOHARD BOYLE. 

